Conventional surgical procedures for pathologies and/or trauma located deep within the body can cause significant trauma to intervening tissues. Open surgical procedures often require a long incision, extensive muscle stripping, prolonged retraction of tissues, denervation, and devascularization of tissue. Most of these surgeries require several hours of recovery room time and several weeks of post-operative recovery time due to the use of general anesthesia and the destruction of tissue during the surgical procedure. In some cases, these invasive procedures lead to permanent scarring and pain.
Minimally invasive alternatives, such as arthroscopic techniques, reduce pain, post-operative recovery time, and the destruction of healthy tissue. In minimally invasive surgery, the site of pathology is accessed through portals rather than through a significant incision, thus preserving the integrity of intervening tissues. These minimally invasive techniques also often require only local anesthesia. The avoidance of general anesthesia reduces post-operative recovery time and the risk of complications.
Minimally invasive surgical techniques are particularly desirable for spinal and neurosurgical applications because of the need for access to locations deep within the body and the danger of damage to vital intervening tissues. For example, a common open procedure for disc herniation, laminectomy followed by discectomy, requires stripping or dissection of the major muscles of the back to expose the spine. In a posterior approach, tissue including spinal nerves and blood vessels around the dural sac, ligaments, and muscle must be retracted to clear a pathway from the skin to the disc. These procedures normally take at least one to two hours to perform under general anesthesia and require post-operative recovery periods of at least several weeks. In addition to the long recovery time, the destruction of tissue is a major disadvantage of open spinal procedures. As a result, many patients may be reluctant to seek surgery as a solution to pain caused by spinal conditions.
In order to reduce the post-operative recovery time and pain associated with spinal and other procedures, micro-surgical techniques have been developed. For example, in micro-surgical discectomies, the disc can be accessed by cutting a pathway from the surface of the patient's back to the disc through a small incision. An operating microscope can be used to visualize the surgical field. Small diameter micro-surgical instruments may be passed through the small incision and between two laminae and into the disc. The intervening tissues are disrupted less because the incision and the exterior-to-interior pathway are smaller. Although these micro-surgical procedures are less invasive, they still involve some of the same risk of complications associated with open procedures, such as injury to the nerve root and dural sac, perineural scar formation, reherniation at the surgical site, and instability due to excess bone removal. A disadvantage of such micro-surgical techniques related to these types of complications is that they do not allow direct visualization of the surgical site by the surgeon.
The development of percutaneous spinal procedures has resulted in reduced recovery time and decreased post-operative pain because they require minimal, if any, muscle dissection and they can be performed under local anesthesia. For example, one such technique is a percutaneous lumbar discectomy using a lateral approach, preferably under fluoroscopic X-ray. Another percutaneous spinal procedure involves decompression of herniated discs with a postero-lateral approach. This approach is a biportal procedure which involves percutaneously placing both a working cannula, by which fragments of the herniated disc are evacuated, and a visualization cannula for inserting an endoscope. This procedure allows simultaneous visualization and suction, irrigation, and resection in disc procedures. However, such conventional procedures are limited because they do not provide direct visualization of the surgical site and because they may require multiple entry portals into the patient. In addition, such lateral and postero-lateral approaches do not address spinal conditions which may require a mid-line approach or the removal of bone or implants.
Endoscopic surgical techniques allow a surgical procedure to be performed on a patient's body through a relatively small incision in the body and with a limited amount of body tissue disruption. Endoscopic surgery typically utilizes a tubular structure known as a cannula which is inserted into a small incision in the body. The cannula holds the incision open and serves as a conduit extending between the exterior of the body and the local area inside the body where the surgery is to be performed. Due to the relatively small size of the passage into the body defined by the cannula, certain surgical procedures, such as posterior discectomies and procedures using steerable surgical instruments, can be difficult to perform using endoscopic techniques.
One percutaneous approach to creating a surgical access passage utilizes a series of increasingly large dilation cannulae. In this technique, a small diameter cannula is inserted percutaneously to a surgical site. A slightly larger diameter cannula is then inserted around the smaller cannula in order to stretch the surrounding tissue. Increasingly larger cannulae, for example as many as a dozen cannulae, can be inserted one at a time, in order of increasing diameter, around the previously inserted cannula so as to incrementally retract surrounding tissue. This approach has the disadvantages of requiring use of a number of sterilized cannulae and traumatizing tissue each time a larger cannula is inserted.
Another approach to creating a surgical access passage, disclosed in U.S. Pat. No. 6,800,084 to Davison et al., involves a tubular cannula having a first tubular portion and a second tubular portion. The second tubular portion comprises an arcuate segment of cannula material rolled into tubular shape and attached to the distal end of the first tubular portion. After the cannula is percutaneously inserted to a surgical site, an expansion tool can be inserted through the cannula. A frustoconical tip of the expansion tool can be used to expand the distal portion of the cannula by unrolling the arcuate segment into a frustoconical shape.
The device and method disclosed by Davison et al. have several disadvantages. Although this approach provides an expanded work area at the surgical site (at the distal end of the cannula), it does not provide a larger, constant cross-sectional diameter along the entire length of the cannula so as to allow direct visualization of the entire operative site by the surgeon. Expansion of the second tubular portion of the cannula requires use of a separate expandable instrument that must be manipulated in numerous positions to fully expand the second tubular portion. The device and method disclosed by Davison et al. also have the disadvantage of lacking a mechanism for effectively maintaining the second tubular portion in its fully expanded position in a frustoconical shape. As a result, the surrounding tissue may begin to move back into the surgical field during a procedure and interfere with both visualization of the surgical site and the surgical procedure itself.
Surgical devices used in minimally invasive procedures often require provision of a light source to illuminate the surgical site. Conventional micro-surgical devices and endoscopic instruments often include a light source, for example, a fiber optic cable, integrated with or attached to the device or instrument. In percutaneous procedures, placing a light source such as a fiber optic cable through the surgical access passage can substantially obstruct the passage such that direct visualization of the surgical site is impeded.
Thus, there is a need for devices and methods that permit enlarged direct visualization of surgical procedures in a percutaneously-accessed surgical work space. There is a need for such devices and methods that provide access to and/or illumination at the surgical site without obstructing visualization of the site. There is a need for such devices and methods that reduce the number of portals into the patient. There is a need for devices and methods that provide for such percutaneous, minimally invasive surgery useful in a variety of applications and approaches.